Instead of running into the water, some beachgoers are running into bright red signs signaling closed beaches due to unsafe swimming conditions. With UW Sea Grant support, UW-Milwaukee environmental toxicologist Sandra McLellan is searching for the source of contaminants along the Lake Michigan coast, hoping to arm management agencies with better information to clean up beaches.
Beach managers post closings when the amount of Escherichia coli in the water exceeds standards recommended by the U.S. Environmental Protection Agency. E. coli is a bacterium that causes minimal health risk to swimmers, but in high numbers it can indicate the presence of other dangerous bacteria and viruses that can sicken beachgoers.
To find out if pollutants originate from humans, McLellan has been checking for resistance in E. coli to antibiotics, which people use and wild animals don’t. Tracing the origins of nonhuman pollutants can be more challenging. Possible sources range from gull droppings in the sand to rainwater that flows to beaches after running off lawns, farms, streets or construction sites, picking up animal waste, fertilizer, pesticides, trash and many other pollutants along the way. To weed through these possibilities, McLellan, a bacterial geneticist, looks for genetic markers in another species of indicator bacteria. Certain types of Bacteroides can be linked to fecal matter from specific host animals, such as cows or humans. next >>